Prior art
Different types of oscillators are known with variable precision as a function of variations in operating conditions of the oscillator, in other words as a function of process, temperature and/or power supply voltage variations.
Thus some oscillators, for example such as quartz oscillators, can give a frequency precision of the order of 1%.
However, one disadvantage of these oscillators is that they are based on the use of at least one external component to increase their precision.
Similarly, some oscillators make use of components such as external resistors or capacitors, to generate a precise time base.
There are also oscillators, for example with a ring structure, that do not require the use of external components.
However, such oscillators usually have a lower precision (of the order of 30%) than oscillators using an external component.
A calibration system then has to be used to improve their precision, for example by adding bits for programming a delay or a capacitance, or using a matrix of fuses that can be burnt out during tests. The precision of such oscillators is of the order of 5%.
However, one disadvantage of these calibration systems is that they require the use of a register to be loaded (for example of the RAM (Random Access Memory) type) when programming bits are added, or a very large circuit surface area (of the order of twice the area of the oscillator) when a fuse matrix is used.